The invention relates to labeled transition metal complexes, labeled chemical or biological entities comprising such complexes, methods for preparing said labeled chemical or biological entities, as well as to specific uses of such transition metal complexes.
The labeling of bio-organic molecules, such as DNA molecules, is desirable for applications in fields such as recombinant DNA technology. In many cases, however, one wishes not to label the nucleic acid macromolecule, but to label a certain nucleotide. The main purpose for labeling nucleotides is that these labeled nucleotides can be incorporated in nucleic acid molecules. This way, the location of the label on the resulting polynucleic acid can be influenced, which is not possible when a label is attached to the macromolecule.
It is known that nucleotides can be linked in a sufficient way to a label by means of a cis-platinum complex. However, such labeled nucleotides are not satisfactorily built in into DNA molecules by DNA polymerase, if at all.
The available alternative methods for labeling a nucleotide, which can be incorporated into a polynucleic acid are the more conventional methods for labeling. However, these methods also have a major disadvantage as they are not suitable for labeling any nucleotide. In some cases, for instance, when only a few residues of a certain nucleotide are present in a certain polynucleic acid, or when the terminating nucleotide residue of a polynucleic acid is to be labeled, it is desired to be able to label any nucleotide. An example of such a conventional method has been described by Dale et al., Biochemistry, 14, (1975), 2447-2457, which method involves direct covalent mercuration as a labeling technique. Dale et el. report that cytosine and uracil may be mercurated at their C5-position under mild conditions. However, they also report that for adenine, thymine and guanine bases negative results were obtained.
Thus, there is a need for a universal labeling system, which is excellent for linking labels and bio-organic molecules, including all different nucleotides, and which also makes it possible to enzymatically build in any nucleotide labeled through said labeling system in a polynucleic acid in an efficient manner.